Impact of multiple air pollutants on probable sarcopenia in the UK population: the mediating role of physical activity and biological aging

Emerging evidence links air pollution to probable sarcopenia (PSA), yet combined effects of multiple pollutants and their mediating pathways remain unclear. We aimed to evaluate both individual and combined effects of air pollutants on PSA, and to explore mediating roles of physical activity and biological aging. Data from 211,808 UK Biobank participants were analyzed. PSA was defined by the EWGSOP criteria. Annual average concentrations of nitrogen oxides (NOx), nitrogen dioxide (NO2), particulate matter ≤ 2.5 μm (PM2.5), particulate matter ≤ 10 μm (PM10), and coarse particles (PM2.5−10) were estimated by land use regression models. Multivariate logistic regression, weighted quantile sum (WQS) analysis, and Cox regression were employed to investigate cross-sectional, combined and longitudinal associations, respectively. Parallel mediation analyses quantified independent contributions of physical inactivity and accelerated biological aging, which was quantified by the Klemera-Doubal method (KDM-BA) and PhenoAge. In cross-sectional analyses, each 10 µg/m³ increase in NOx (odds ratio [OR]: 1.11, 95% confidence interval [CI]): 1.08–1.14), NO2 (1.03, 1.02–1.04), PM2.5 (1.41, 1.16–1.72), and PM10 (1.35, 1.22–1.50) was associated with elevated PSA risk. The combined effects, indicated by WQS index, yielded an OR of 1.14 (95% CI: 1.11–1.17). Longitudinal analyses over 5.76 years further confirmed an increased incident risk. Physical inactivity significantly mediated the associations across both cross-sectional (7.0-10.2%) and longitudinal models (10.9%), while accelerated biological aging was significant only cross-sectionally (9.7–30.7%). Individual and combined exposures to air pollutants elevate PSA risk, partially mediated by physical inactivity and accelerated biological aging, underscoring the need for improved air quality, active lifestyles and healthy aging to mitigate sarcopenia burden.